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A tokamak, which is the most successful device now on the road to controlled fusion, has the major disadvantage of pulsed operation because of a need to induce a toroidal current in the plasma. The application of rf to drive the current in steady-state tokamak reactors has been considered by a number of authors. 1 " 5 A method of producing continuous current carried by electrons in the tail of distribution function via quasilinear Landau damping of high-phase-velocity rf waves near the lower hybrid (LH) frequency has been proposed. 4,5 The linear and quasilinear Landau damping of slow electrostatic waves near LH frequency has been confirmed in a linear test device 6 and in the LH electron heating experiment on the tokamak (Doublet IL4). 7 These experiments provide a physical base for understanding the quasilinear Landau damping in the toroidal plasma with a relatively high electron temperature. Recently, the current generated by the unidirectional electron plasma waves has been observed in linear devices 8 * 9 and a toroidal device. 10 These experiments have been carried out in a plasma with a lower electron temperature, in which a transfer of momentum from LH waves to electrons via collisional absorption is significant.In order to make effective coupling between the LH waves and electrons, it is necessary to avoid the deposition of the rf energy into ions resulting ^. Mandelbrot, Fractals: Form, Chance, and Dimension (Freeman, San Francisco, 1977). e from the linear mode conversion and the excitation of parametric instabilities. The previous experiments on the rf ion heating indicated that i-for w Q /w lh {$) ^ l c 6 the ions did not interact with i the rf waves and the parametric decay instabilities almost disappeared, 11,12 where ou 0 is the frequency of the applied rf field and oo lh (0) is the LH QS frequency at the center of the plasma column. In this Letter, we report the experimental study on s the coupling between the rf waves and electrons under the conditions of oo 0 /uo lh (0) < 2 and the relatively high electron temperature in a tokamak. J-The experiment, with a 750-MHz rf source, e 6 was performed in the J FT-2 (JAERI Fusion Torus) i tokamak, which was a conventional tokamak with a major radius of JR 0 = 90 cm and a minor radius of a = 25 cm. The experimental setup and the discharges were reported in detail, 13 and hence will be described only briefly here. In the present l-experiment, the following discharge was used as a magnetohydrodynamically stable operation; toroidal magnetic field B t = 14 kG, plasma current I p = 3Q kA, mean line-of-sight electron density n ^3xl0 12 cm -3 , central electron temperature T^ -(250 eV)/k and effective ionic charge Z e ff of 2-5. The working gas was deuterium. The wave-3 guide array employed here consists of four indei pendently driven waveguides mounted 1.5 cm 5 away from the plasma edge, which is defined by It is observed that the waves launched from a phased array antenna of four waveguides couple effectively with electrons under the condition of oo 0 /oo lh (...

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Results are presented of the first Lower Hybrid Current Drive (LHCD) experiments in JT-60. 2 MA of RF driven current is successfully produced for the first time in a reactor grade tokamak. The magnetic divertor works quite well in eliminating the impurities released by the current carrying fast electrons which have allowed the generation of the reactor relevant RF current in a very low density plasma. The efficiency which is defined asr?cD = n e RlRF/PLHO u19 m " 3 A-W" 1 ), reaches values of 0.8 to 1.7. NBI heating enhances the current drive efficiency by a factor of 1.5, and LHCD improves the confinement time of high power NBI heated plasma. The key to confinement improvement is found to be the active control of the current profile by LHCD.

We performed a hand-assisted laparoscopic resection of the distal stomach for treatment of gastric cancer with use of an abdominal wall-lift method. The surgeon's left hand, which was inserted through a right lower quadrant incision, was extremely useful in accomplishing D2 lymph node dissection, application of a pursestring instrument, and approximation of a circular stapler to carry out a Billroth I anastomosis. Abdominal wall-lift enabled us to perform the gastrectomy without any concern about gas leakage. The combination of the wall-lift method and hand assistance seems to further enlarge the possibilities of laparoscopic procedures, especially in gastrointestinal surgery.

Results from the JFT−2a (DIVA) experiments made with a separatrix magnetic surface are described. The main conclusions are: (1) A separatrix magnetic surface is stably located inside the material surface. (2) A plasma enclosed in a separatrix magnetic surface is similar to that of a conventional tokamak as far as the magnetohydrodynamic properties are concerned. (3) Measured parameters of the main plasma column are consistent with those expected from a conventional tokamak. (4) The electron density and temperature in the scrape-off layer are about ten times less than the values at the center of the main plasma column. (5) Heat and particle fluxes to the divertor region are axisymmetric and several times less than those of the total loss fluxes from the main plasma column. (6) Runaway electrons are well guided to the divertor region.

ICRF heating of impurity-free tokamak plasmas is studied in DIVA. The frequency is fixed at 25 MHz, which is a second-harmonic cyclotron frequency of deuteron with a toroidal magnetic field of 16.4 kG. The toroidal field BT and the ratio of proton-to-deuteron density ϵp are varied over ranges of 12 ⩽ BT ⩽ 19 kG and 2 ⪅ ϵp ⪅ 40%, respectively. The most favourable ion heating is obtained at BT = 18 kG and ϵp = 5 ∼ 10%. Ion temperature increases from 200 to 300 eV were measured by charge-exchange neutral analysis and also by spectroscopy, where 100 kW RF net power were applied. The results are consistent with mode-conversion theory.

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